Apparatus for reducing sheath currents



A ril 1, 1930. F. J. WHITE 1,752,318

APPARATUS FOR REDUCING SHEATH CURRENTS Origina] Filed April 8, 1927 i V z z r J (2 7 3 4 i I VI l7 /4 1 \la I I 2 INVE T l @4022 1o nating current throug Patented Apr. 1, 1930 UNITED STATES PATENT OFFICE MCI! J. WHITE, 01' BROOKLYN, NEW YORK, ASSIGNOB T was OKONITE comm, 0F PASSAIC, NEW JERSEY, A CORPORATION 01 NEW ERSEY APPARATUS FOB REDUCING BREATH CUBRENTB Orlrlnal application fled April 8, 1987, Serial 80.181318. Divided and this application fled Iebmry 88, 1928. Serial No. 257,678.

This invention relates to electric apparatus, and particularl to a paratus for use in connectlon with ca les or carryin alternating or pulsating currents, and has or one of its objects the provision of means for reducing the currents induced in the sheath or other cover or coverings of such cables and to be referred to hereinafter as sheath currents.

It is well known that the passage of alterh a single conductor cable, or the unbalancm of alternating currents in a multiple con uctor cable, induces an electromotive force in I metallic cover which, if this sheath or metallic cover 1s not connected to ground or to other conducting paths, may produce a dangerous difference of potential between the cable sheath and ad acent structures, and it is a further object of my invention to reduce or, if desired, to neutralize this action.

If this sheath is metallically connected with other conducting paths, so as to form a complete circuit, a current is set up. This socalled sheath current, in addition to the losses in transmission it causes, has an appreciable effect on the heating of the cable, and hence reduces the permissible current 1n the conductor.

In order that these sheath currents may be reduced and it) tle sari? ltimebtlo rmit of ounding' or n o t e ea c, propose iii divide the sheath f the cable into discontinuous lengths suitably insulated from each other and so to connect said discontinuous lengths by suitable conductors that the electromotive force induced in one section, is opposed to the electromotive force induced 1n an adjacent section or sections. Additional to this construction I may provide a member of magnetizable material in position to be magnetlzed by current flowin in the conductor or conductors of the cable. his member may or may not be constructed with an air gap but in any event the conductors above mentioned toget er with one of the sheath sections will function as a coil for the magnetizable mem- In my condin application Serial No. 181,916, file Apri 8, 1927, of which this application is a division, I describe a constructhe cable sheath or' tor cables proportional to the vector sum of the currents, it is obvious that by properly connecting the sections of the sheath to each other, the effect of the elecromotive force induced in any specified length of sheath may be neutralized. In those instances where a member of magnetizable material is provided.

about a sheath section this member should'be proportioned as to operate below the saturation point if it is desired to have complete neutralization at all loads. If, however, complete neutralization at the heavier loads is not desired then the core may work beyond the saturation point.

In the drawings accompanying this application Fig. 1 shows one embodiment of my invention and Fig. 2 shows another embodiment of my invention.

Both figures of the drawing are more or less dia ammatic.

Fig. 1 I show a cable 1, which may be either 0 the single conductor or the multiple conductor type, the sheath of which is composed of sections, 2, 3, 4, 5, 6, 7, 8, etc., adacent sections being insulated from each other as indicated at 9. Attached to the section 2 is one end of a conductor 10, the other end g connected to the end of the section 3 remote from the section 2. To the op osite end of this section 8 is connected a condiictor 11, the other end of which is connected to the end of the sheath section 4 adjacent the section 3. The conductor 10 is grounded at 12.

The end of the sheath sectlon 4 ad 'acent the sheath section 5 is grounded as in icated at 13 and to this ground and to the end of sheath section 5 remote from the sheath section 4 is connected a conductor 14. Connectof the magnetic circuit of the member 19 the ed to the opposite end of sheath section 5 is same efiect electrically could be obtained.

connected a conductor 15, the opposite end In both embodiments of my invention, of which is connected to the end of section therefore, I have pro 'ded a construction in 5 6 adjacent the section 5. The opposite end of which the electromotive force induced in one 70 the section 6 is grounded as indicated at 16, sheath section is opposed to the electromotive and connected to this ground and the end force induced in another sheath section, speof sheath section 7 remote from the sheath seccifically an adjacent sheath section. In the tion 6 is a conductor 17 while 18 designates a construction of Fig. 2, however, I provide conductor connecting the end of sheath secfor the electromotive force induced in one 1 tion 7 adjacent sheath section 6 and the end sheath section to oppose the electromotive of sheath section 8 adjacent sheath section 7. force induced in ad acent sheath sections.

This provides a construction, therefore, ap- As above pointed out, and as will be clear plicable to single conductor or to multiple to those skilled in this art, my invention is conductor cables in which the electromotive ap licable to multiple conductor cables as w force induced in one sheath section is opposed we 1 as single conductor cables, and the apto the electromotive force induced in another pended claims, it is to be clearly understood, section, specifically an adjacent section. For are to be so interpreted. example the sheath sections 5 and 6 are so WhatIclaim is 20 connected to each other by the conductor 15, 1. An insul ated cable 111 which the sheath 35 that the electromotive force induced in the hereof 15 dlvlded into discontinuous lengths sheath section6dueto current in the conductor insulated from each other, and conductors dior conductors of the cable is opposed by the rectly connecting the said sheath lengths so electromotive force induced in sheath sech h electromotive force i d i one ti 5, length is opposed to the electromotive force 90 With the above construction the flow of induced in another length of the same sheath sheath current is reduced and may be oi the Seine cabieneutralized provided the sheath sections are 2. An insulated cable i which the sheath of proper lengths t b l h th thereof is divided into discontinuous lengths To make this construction commercially insulated f each 0 ,a d conductors as practicable it will be understood that the lonrectly connecting adjacent lengths so that the gitudinal gpertion f th o d t 10, 11, electromotive force induced in one len h is etc., must placed some distance from or opposed to the electromotive force in uced magneticall S ield d fro th n ti fin an ad acent length of the same sheath of feet of the current in the conductor or conthe Same f loo ductors of the cable. 3. An insulated cable in which the sheath While in the construction above described t r i iv in o dis on in ous lengths the flow of sheath current can be reduced and Insulated f tn e h other, and conductors even neutralized if desired by proper division con ectm an intermediate sheath lengthto of the sheath, a construction such as illusad acent en he so that the electromotive m5 trated in Fig. 2 may be preferred in some inforce induce in the intermediate length opstances. poses the electromotive force induced in In Fig. 2 I have placed a member 19 of magengths of the same sheath ad acent the internetizable laminated material and having an me iate length.

adjustable air ap 20 about the section 3 of 4. An insulated cable n wh ch the sheath no the cable sheath and in inductive relation to thereof 18 divided into discontinuous lengths the current flowing in the conductor or coninsulated from each other, a member of magductors of the cable thereby increasing the net'izable material disposed about one of said induced voltage in sheath section 3. While l th d conductors f connecting th the conductors l0 and 11 so connect sections 2, l t ti d h th l th t dj t 116 3 and 4 that the electromotive force induced sheath 1engths,said conductors and the sheath in the Section 3.13 o to the eleftromotwe length about which the magnetizable member force induced in t e ad acent sections 2 and is disposed cooperating w said mag 4, the XIOVISIOD of the member 19 increases netizable member.

the in uced voltage in the sheath section 3 An insulated cable in which the sheath 120 and grunts of relatively short length of thereof is divided into discontinuous lengths it agg ggi g ih fig zl 19 is of insulated from each other, a member of maghminamd construction with adjustable n. netizable material, conductors for connecting 60 ap 20, adjustment of this gap being effected 1 fwent 511994511 l g 1 g- 1:5

by adjustment of the laminations about the nPi'ilzable material ng 1n Inductive relaivoted connection 21. On the other hand tlOn t c rr nt Passing through the con.

the laminations com osing this member could ductors of the cable and adjacent one of said be solid rings, and y changin the number sheath lengths, said sheath length and said 66 of rings or laminationsto vary t ereluctance conductors cooperating with said magnetizno able member to function as a coil for the magnetizable member.

6. An insulated cable in which the sheath thereof is divided into discontinuous lengths insulated from each other, a laminated mag- 5 netizable member surrounding an intermediate sheath length and conductors connecting said intermediate sheath length to adjacent lengths.

7. An insulated cable in which the sheath thereof is divided into discontinuous lengths insulated from each other, a magnetizable member, disposed about an intermediate length, the reluctance of the magnetic circuit of said magnetizable member being adjustable, and conductors connecting the said intermediate sheath length to others of said sheath lengths and cooperating with the intermediate sheath length and said magnetizable member.

This specification signed this 23rd day of February, 1928.

FRANCIS J. WHITE. 

